Transformation of phosphorus compounds obtained as by-products

ABSTRACT

A process whereby substantially low-valent phosphorus-containing compounds in waste by-products obtained in the manufacture of mineral and organic phosphorus compounds are converted into useful phosphoric acid, polyphosphoric acid, or corresponding alkali metal salts thereof despite the presence of partially noncombustible material, organic pentavalent compounds, and nonphosphorus-containing compounds within said material; by introducing the by-products into an elemental phosphorus-oxygen flame having excess oxygen, the by-products being introduced in an amount so as not to exceed 50 percent by weight of the elemental phosphorus being burned in said flame.

United States Patent Harnisch et al., 1451 Apr. 18, 1972 [54]TRANSFORMATION OF PHOSPHORUS v COMPOUNDS OBTAINED AS BY- Y R f rencesCited PRODUCTS UNITED STATES PATENTS [72] Inventors: l ilztliissgrmglinigh 515;? 38522} 5,050,374 8/1962 Burt et al. ..23/165 AKarl Traulsen, Knapsack near g 2,925,326 2/1960 Pieper et a1 ..23/ 165Gerhard Harflapp Hermulheim near Primary Examiner-Oscar R. VertizCOlQEflEflHM Germany a .H. mam;mfiina chafl FfRFdEFrT [73] Assignee:Knapsnck Aktiengesellschaft, Knapsack A""" Y and Hull I near Cologne,Germany 22 F] d M 14 1965 [57]- ABSTRACT 1 1e ay A process wherebysubstantially low-valent phosphorus-con- PP ,994 taining compounds inwaste lay-products obtained in the 1 manufacture of mineral and organicphosphorus compounds Relaled U's'Apphcamm Data are converted into usefulphosphoric acid, polyphosphoric [63] Continuation of Ser. No. 519,946,Jan. 11, 1966 acid, or corresponding alkali metal salts thereof despitethe abandoned presence of partially non-combustible material, organicpentavalent compounds, and non-phosphorus-containing com- 0 ForeignApplication priority m pounds within said material; by introducing theby-products into an elemental phosphorus-oxygen flame having excess ox-Feb. 17, 1965 Germany .K 55 302 ygen, the byproducts being introduced inan amount so as not to exceed 50 percent by weight of the elementalphosphorus [52] US. Cl ..23/l65 being burned in i flame. [51] Int. Cl...C0lb 25/12 [58] Field of Search ..23/165 8 Claims, No DrawingsTRANSFORMATION OF PHOSPHORUS COMPOUNDS OBTAINED AS BY-PRODUCTSCROSS-REFERENCE TO RELATED APPLICATION The present application is acontinuation of US. application Ser. No. 519,946 filed Jan. 1 l, 1966,now abandoned.

The present invention relates to a process which enables phosphoruscompounds, such as often obtained as byproducts in the manufacture ofmineral and organic phosphorus compounds and such as most frequentlycontain low-valent phosphorus, to be transformed into useful products.Such by-products could not be utilized heretofore for reasons of economyand because of undesirable contamination of the waste water and theatmosphere. It is, therefore, an object of the present invention toprovide a process enabling such waste products to be utilizedcommercially.

It is already known that so-called phosphorus sludge of the emulsiontype obtained on condensing phosphorus vapors resulting from phosphorusproduction by electrothermal means, can be subjected to combustion bymeans of a flame fed with pure liquid phosphorus and oxygen to betransformed into pure P or pure orthophosphoric acid. Still further, ithas already been proposed to prepare phosphates by spraying a solutionof an alkali metal hydroxide or carbonate and further alkali metal saltshaving a volatile anion into a phosphorus flame with the resultantformation of solutions of alkali metal phosphates when equivalentproportions of starting material are used.

It has now been found that phosphorus compounds obtained as by-products,such as mineral and organic phosphites, phosphates, phosphonates,hypophosphites, phosphorous acid, phosphines or the like, optionallycontaminated with additional compounds free from phosphorus, can alsoreadily be transformed into compounds of pentavalent phosphorus by beingsubjected to combustion by means of a flame fed with elementaryphosphorus and a gas containing free oxygen in excess with respect tothe phosphorus.

Depending on the reaction conditions and the phosphorus compounds to betransformed, either phosphoric acid or polyphosphoric acids or thealkali metal salts of such acids can be obtained provided that the P 0formed as an intermediary compound is transformed in conventional mannerinto the compounds mentioned above. It has unexpectedly been found thatthe smooth oxidation of phosphorus to P 0 is not affected, that thephosphorus compounds to be transformed practically undergo completeoxidation to give compounds of pentavalent phosphorus, and thatconstituents of organic nature are entirely converted into CO In otherwords the final products obtained are free from contaminants, such asorganic substances, cracking products thereof, carbon or the like.

This considerable advantage of the process of the present inventioncould not be forseen since contrary to phosphorus sludge as previouslyused the substances transformed in the phosphorus flame are partiallynon-combustible and have no readily volatile anion unlike the compoundspreviou sly used.

The phosphorus compounds to be transformed can be reacted in thephosphorus flame in proportions practically limited by the oxidizingcapacity of the flame; generally, however, the phosphorus compoundsshould be used in a proportion not greater than 50 percent by weight,and preferably in a proportion of 9 to percent by weight, referred tothe elementary phosphorus.

When the starting compounds are used in liquid form, the phosphoruscompounds should conveniently be mixed with molten phosphorus and theresulting mixture transformed in conventional manner with a gascontaining free oxygen into compounds of pentavalent phosphorus.

The phosphorus compounds can be used in liquid form, i.e. in the form ofa melt or solution or suspension in an aqueous or organic solvent, theconcentration of the solution or suspension being not critical. Whenused in gas form, the phosphorus compounds are most convenientlyinjected centrally or from the outside into the phosphorus flame in amanner such that the total quantity of phosphorus compounds isintroduced into the flame cone.

EXAMPLE 1 Transformation of Sodium Phosphite (Na flPo About 10.2 percentby weight of a 55 percent aqueous sodium phosphite solution weresubjected for a period of time of 5 5% hours to combustion withphosphorus and the resulting P O was absorbed to produce polyphosphoricacid by the process described in US. Pat. No. 3,387,929.

As taught therein, the P 0 was absorbed in two stages by means ofphosphoric acid of low concentration. The bulk of heat set free duringthe combustion reaction was dissipated in a first zone while a portionof the P 0 formed was absorbed concurrently therewith by causingphosphoric acid, which can be cooled by means of a suitable coolingsystem, to flow in a cycle I through the said zone. The balance portionof P 0 was absorbed subsequently in a second zone and the residualreaction heat was absorbed-concurrently therewith by causingpolyphosphoric acid to travel in a cycle II through the said second zoneand through an appropriate cooling system, the polyphosphoric acidcontaining P 0 in a concentration higher than the acid cycled in cycleI.

The content of reducing substance in the polyphosphoric acid was:

before addition after addition incyclel 0.l5% 0.l2% in cycle ll 0.0030.02 k

Non-oxidation of the phosphite would have resulted in the content ofreducing substance being increased in the two cycles to a value of 0.30.4 percent.

EXAMPLE 2 Transformation of Sodium I-Iyposhosphite (NaI-I PO About 1 1.1percent by weight of a 50 percent aqueous sodium hypophosphite solutionwere added in measured quantities for a period of time of 3% hours. Theprocedure was otherwise the same as that described in Example 1. Thecontent of reducing substance in the polyphosphoric acid was:

before addition after addition in cyclel 0.05 v 0.ll in cycle n 0.020.03 Theoretical value for non-oxidationz 0.4-0.5

EXAMPLE 3 Transformation of a Waste Product Obtained in PhosphineProduction.

The product was composed approximately of: 14 NaH PO 9 Na i-IP0 7percent unknown phosphorus products dissolved or suspended in amethanol/water-mixture.

9.1 percent by weight were added for a period of time of 4% hours. The P0 was absorbed in the manner described in Example 1.

before addition after addition incycleI 0.ll% 0.13% in cycle II 0.030.05

EXAMPLE 4 Transformation of Organic Phosphite Waste.

A distillation residue was used which chiefly contained methylphosphites and showed the following analytical data:

total content of P O 76.8 reducing substance, determined iodo- 41.0metrically and calculated as H,PO,

total C-content 9.5 7:

before addition after addition in cycle I 0.04 0.03 Theoretical valuefor non-oxidation: 0.35 1%.

EXAMPLE 5 Transformation of H -,PO -,-waste.

A 70 percent aqueous solution of contaminated phosphorous acid was addedto the phosphorus. About 10.9 percent by weight were added for a periodof time of 4 hours. The P formed was absorbed in the manner described inExample 1.

The content of reducing substance in the polyphosphoric acid was:

before addition after addition in cyclcl 0.06 7; 0.05 70 in cycle II0.04 k 0.02 Theoretical value for non-oxidation: 0.6-0.8 percent.

EXAMPLE 6 Transformation of Organic Phosphite-waste by SeparateInjection into the Phosphorus Flame.

The distillation residue of Example 4 was injected through awater-cooled nozzle into the cone of the phosphorus flame and theresulting P,,O was absorbed in orthophosphoric acid.

9.3 percent by weight were added for a period of time of l 1 hours.

The content of reducing substance in the orthophosphoricacid formed was:

before the addition 0.03 during and after the addition 0.06-0.08Theoretical value for non-oxidation2 0.9 9?.

EXAMPLE 7 Transformation of Sodium Phosphite (NaJiPO for Making MoltenPhosphates.

About 9.8 percent by weight of a 55 percent aqueous sodi- 5 um phosphitesolution were subjected for a period of time of 6 hours to combustionwith phosphorus and the resulting P 0 was absorbed for making sodiumphosphates (molten phosphates) by the process disclosed in US. Pat.application Ser. No. 375,388, now abandoned.

The content of reducing substance in the phosphorus melt was:

before addition 0.0l

after addition 0.01 it:

phosphorus compounds a phosphorus waste byiproduct capale of reducingphosphorus in compounds, e said waste product containing about 41percent of reducing substances determined iodometrically and calculatedas H PO and consisting of a distillation residue of methyl phosphitewhich comprises introducing into a phosphorus oxygen flame the saidwaste by-product, the said phosphorus oxygen flame having excess oxygenwith respect to the elementary phosphorus burned, the amount of wasteby-products introduced into the flame not exceeding 50 percent by weightrelated to the elementary phosphorus burned to obtain the recoverablepentavalent phosphorus compounds.

2. The process as claimed in claim 1, wherein the waste products to betransformed are used in a proportion of 9 15 percent by weight, relatedto the elementary phosphorus.

3. A process as claimed in claim 1, wherein waste product compounds inliquid form are so injected into the phosphorus flame that the totalquantity thereof is introduced into the flame cone.

4. A process as claimed in claim 1, wherein gaseous waste products areso injected into the phosphorus flame that the total quantity thereof isintroduced into the flame cone.

5. A process as claimed in claim 1, wherein the waste products areintroduced centrally into the phosphorus flame.

6. A process as claimed in claim 1, wherein the waste products areintroduced from the outside into the phosphorus flame.

7. A process as claimed in claim 1, wherein the waste products are usedin molten form.

8. A process as claimed in claim 1, wherein the waste products are usedin the form of solutions and suspensions of aqueous and organicsolvents.

2. The process as claimed in claim 1, wherein the waste products to betransformed are used in a proportion of 9 - 15 percent by weight,related to the elementary phosphorus.
 3. A process as claimed in claim1, wherein waste product compounds in liquid form are so injected intothe phosphorus flame that the total quantity thereof is introduced intothe flame cone.
 4. A process as claimed in claim 1, wherein gaseouswaste products are so injected into the phosphorus flame that the totalquantity thereof is introduced into the flame cone.
 5. A process asclaimed in claim 1, wherein the waste products are introduced centrallyinto the phosphorus flame.
 6. A process as claimed in claim 1, whereinthe waste products are introduced from the outside into the phosphorusflame.
 7. A process as claimed in claim 1, wherein the waste productsare used in molten form.
 8. A process as claimed in claim 1, wherein thewaste products are used in the form of solutions and suspensions ofaqueous and organic solvents.